This invention relates to a settable printing apparatus. In particular, but not exclusively, the invention relates to a dater for a postage meter. A dater is defined as those components forming part of or operatively connectable to a postage meter which enable a user of postage meter to set the date to be printed by printwheels of the dater. The dater also has a function in providing a signal indicative of the date set, to enable verification of the accuracy of this date. This verification may be accomplished either by visual inspection of a displayed date; or by means of suitable processing circuitry in the logic board of the postage meter.
The invention also relates inter alia to a value printing (franking) mechanism for a mail processing apparatus such as a postage meter. A franking mechanism is similar to a dater in that it employs a settable gear train linked to a number of printwheels for franking a desired postage value.
The invention also is of use in other settable mechanisms in mail processing apparatus such as postage meters, folders, inserters and conveying apparatus.
Many postage meters employ a number of thumbwheels which are settable by the operator in accordance with the desired date. Incremental rotation of the thumbwheels causes incremental rotation of the dater printwheels, by means of a gear train. It is known to provide a dater which is constituted in part by an optical encoding mechanism which is capable of detecting the settings of the thumbwheels.
Previously proposed daters of this kind have employed encoding marks at various positions on the thumbwheels, and a retro-reflective light sensor capable of detecting whether a light or a dark portion is facing it. If the processor of the postage meter has been programmed appropriately, it is possible for the signals from the sensor to be interpreted as identifying a particular setting of one of the thumbwheels.
Alternative arrangements have been proposed, in which, for example, physical projections extending outwardly of the thumbwheels have been used to provide an optical encoding mechanism.
However, such known daters suffer from numerous disadvantages.
Firstly, it is necessary to provide a sensor circuit and a set of optical encoding marks for each thumbwheel. (Usually there are at least three thumbwheels in a dater, one for setting the day, one for setting the month and one for setting the year to be printed. Sometimes, two "day" thumbwheels are provided, one for setting the day decade and one for setting the day unit. Franking and other printing mechanisms may employ further thumbwheels.) Thus, the circuitry and physical arrangement of known daters are complicated.
Furthermore, the programming of a processor to which the dater is connected has to provide an absolute measurement of the set position of each thumbwheel. Thus, it is necessary to define a home position for the thumbwheel, and it may be necessary to include a non-volatile memory in the processor so that the dater does not have to be re-set every time the postage meter is switched on. It will additionally be appreciated by those skilled in the art that such an arrangement can lead to erroneous readings of the settings of the thumbwheels.
Moreover, since a plurality of sensors is required, the processing of data signals from the dater can be a comparatively lengthy process, particularly in low-cost postage meters where sequential processing of signals from the respective sensors is employed.